1. Field of the Invention
This invention relates to a multi-component microcircuit package adapted to receive an electronic microcircuit and which is particularly adapted for hermetic closure by securing a lid member thereto. The present invention also relates to the method of forming such a microcircuit package.
2. Description of the Prior Art
In the art of enclosing microcircuits in an environmentally secure package, most applications employ a rectangular or square box-like metal package having a one-piece side wall or frame mounted upon a base. Apertures in the side wall allow for passage of leads out of the package, usually through glass seals. The package is closed by sealing a lid to the upper surface of the side wall after the microcircuit substrate and associated electronics are placed inside the package. For some applications, however, especially where production quantities are small or time limits are such that the necessary tooling is not practical, manufacturers of microcircuit packages have resorted to a multi-component package construction method. In the prior art multi-component process four separate side wall metal components are assembled into a composite frame, for example, by brazing. This composite frame is employed in the same manner as the one-piece frame which is more widely used. The multi-component method can be used to make either a plug-in package or a flat package.
While the multi-component method of manufacturing all metal packages has filled a particular need as described above, there are serious problems with its application. As a result of the bonded construction, the upper surface of this package contains a number of potential irregularities at the brazed junction between the component parts. These irregularities result from the frame component mismatch and/or braze undercut. While the tolerances that can be achieved by this method are suitable to form a package for some applications, most applications involving the use of all metal packages require high reliability. For this reason, it is extremely important that the packages are able to be easily hermetically sealed. The multi-component package, with its top surface irregularities due to mismatch or brazed undercut, is very difficult to hermetically seal with a metal lid using solder. Moreover, it is virtually impossible to seal such a package by welding. Since most applications of a commercial nature require welding, use of the multi-component package method has been primarily limited to prototype purposes.
Thus, it would be of great value to the art if one were to produce a microcircuit package having the flexibility, ease of manufacture, and low cost of the multi-component package construction and the reliability of hermetic closure of the one-piece frame construction.